Immunodeficient mice have been used extensively as a means to grow both normal and transformed cells and/or tissues of various lineages in an in vivo environment. These in vivo models are helpful for many areas of cancer research. To this end, UCLA has established an immunodeficient mouse core laboratory which breeds and houses sever combined immunodeficient (SCID) mice, and provides housing for nude (athymic) mice for biomedical research. In this facility, investigators can introduce normal or transformed tissues of human or murine origin into immunodeficient mice that will not reject the implanted tissues. Consequently, experiments can be performed which provide insights into how these cells behave in vivo and address experimental therapeutic protocols. The nude/SCID mouse core will help the investigators in all 5 components of this Program Project through the following specific aims: 1. To provide SCID mice at reduced costs to Investigators in the Program Project. 2. To maintain an appropriate working laboratory for biosafety level 2 (BSL-2) animal experiments related to this Program Project, which will include appropriate housing for nude and SCID mice, surgical equipment and supplies. 3. To provide animal maintenance and technical assistance for in vivo experiments related to this program project. 4. To provide expertise/consultation on animal experimentation and surgical techniques required for the proposed studies. This facility provides a clean barrier facility with appropriate equipment and supplies at minimal expense to investigators. In addition, animals are maintained and inspected by Core personnel. These personnel are also available to assist in animal manipulations. In vivo studies are important in all components of this application, thus this Core will provide a valuable service to this Program Project.